Klebsiella pneumoniae-Derived Extracellular Vesicles Impair Endothelial Function by Inhibiting SIRT1

Academic Background

Hypertension is a global health issue with a complex pathogenesis involving multiple factors. In recent years, the role of gut microbiota in hypertension has garnered significant attention. Studies have shown that dysbiosis of the gut microbiota is closely related to the development of hypertension. Specifically, Klebsiella pneumoniae (K.pn), a common Gram-negative bacterium, has been found to be associated with the progression of hypertension. However, the specific mechanisms by which K.pn affects endothelial function remain unclear. Endothelial dysfunction is a critical early event in the pathogenesis of hypertension, and bacterial extracellular vesicles (BEVs) play a key role in regulating host cell functions. Therefore, this study aimed to investigate the effects of K.pn-derived extracellular vesicles (K.pn EVs) on endothelial function and the underlying mechanisms.

Source of the Paper

This paper was co-authored by Xinxin Li, Jinghua Cui, Zanbo Ding, and others, affiliated with institutions such as Beijing Anzhen Hospital and the Microbiology Department of the Capital Institute of Pediatrics. The paper was published in 2025 in the journal Cell Communication and Signaling under the title “Klebsiella pneumoniae-derived extracellular vesicles impair endothelial function by inhibiting SIRT1.”

Research Process and Results

1. Effects of K.pn on Endothelial Function

The study first evaluated the effects of K.pn on endothelial function in mice through in vivo experiments. Researchers administered K.pn to 10-week-old C57BL/6 mice via gavage for four weeks. The results showed that K.pn significantly attenuated acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR) and increased superoxide anion production in endothelial cells. These effects could be reversed by the ROS inhibitor Tempol and the SIRT1 activator Resveratrol, suggesting that K.pn-induced endothelial dysfunction may be related to excessive ROS generation and endothelial cell senescence.

2. Isolation and Characterization of K.pn EVs

Next, researchers isolated K.pn EVs from K.pn culture medium using ultracentrifugation and characterized them using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot. The results showed that K.pn EVs exhibited a typical spherical morphology with an average diameter of approximately 100 nm and were enriched with bacterial outer membrane protein OmpA and lipopolysaccharide (LPS). Additionally, fluorescence labeling experiments confirmed that K.pn EVs could be taken up by human umbilical vein endothelial cells (HUVECs).

3. Effects of K.pn EVs on Endothelial Function

Researchers assessed the effects of K.pn EVs on endothelial function through in vivo and in vitro experiments. The results demonstrated that K.pn EVs significantly attenuated endothelium-dependent relaxation and promoted endothelial cell senescence and superoxide anion production. Furthermore, K.pn EVs increased systolic and diastolic blood pressure in mice. These effects could be reversed by the ROS inhibitor Tempol and the SIRT1 activator Resveratrol.

4. Effects of K.pn EVs on SIRT1 and Related Proteins

To explore the mechanisms by which K.pn EVs affect endothelial function, researchers examined the expression of proteins related to endothelial function, endothelial cell senescence, and ROS generation. The results showed that K.pn EVs inhibited the expression of SIRT1 and phosphorylated endothelial nitric oxide synthase (p-eNOS) while promoting the expression of p53, endothelin-1 (ET-1), NADPH oxidase-2 (NOX2), and cyclooxygenase-2 (COX-2). Overexpression or activation of SIRT1 reversed these protein changes induced by K.pn EVs and improved endothelial dysfunction.

Conclusions and Significance

This study is the first to reveal the role of K.pn EVs in endothelial dysfunction and to elucidate the critical role of SIRT1 in this process. The findings indicate that K.pn EVs impair endothelial function by inhibiting SIRT1 expression, leading to endothelial cell senescence, increased ROS generation, and endothelial dysfunction, thereby potentially promoting the development of hypertension. These findings provide new insights into the pathogenesis of K.pn-related vascular diseases and offer potential therapeutic targets for clinical intervention.

Research Highlights

1. Novel Discovery: First to reveal the role of K.pn EVs in endothelial dysfunction and the critical role of SIRT1.
2. Multi-Level Experimental Design: Comprehensive evaluation of the effects of K.pn and K.pn EVs on endothelial function through in vivo and in vitro experiments.
3. Potential Therapeutic Target: Activation or overexpression of SIRT1 can reverse K.pn EV-induced endothelial dysfunction, providing new avenues for hypertension treatment.

Additional Valuable Information

This study also compared the effects of K.pn EVs and Escherichia coli (E. coli) EVs on endothelial function, finding that E. coli EVs had no significant impact on endothelial function at low concentrations but could induce inflammatory responses at high concentrations. This finding suggests that the effects of different bacterial EVs on endothelial cells may depend on their concentration and cellular responses.

This study provides new perspectives on the pathogenesis of K.pn-related vascular diseases and offers potential therapeutic targets for clinical intervention.